In the will-they-won’t-they saga of the traditionalist breakaway group SSPX reconciling with Rome, there always seems to be a last-minute snag or ugly revelation that scuppers the deal.

The most recent was in March 2012, when the Society of Pius X, a wealthy schismatic group with 600 priests in 37 countries, rejected Benedict XVI’s offer of an Opus Dei-type personal prelature in exchange for accepting certain criteria for the interpretation of Catholic doctrine.

SSPX, which regards as heresy the Second Vatican Council’s teachings on religious freedom and other faiths, demanded, as it always does, that if Rome wanted them back, they would have to take them as they were. And to make clear this wasn’t just an argument about the 1960s, they cited Benedict’s hosting of an inter-religious summit in Assisi and even his beatification of Pope John Paul II as additional stumbling blocks.

The traditionalists’ current leader, Archbishop Bernard Fellay, declared at the time that “it is our duty to continuously go [to Rome], knock at the door, and not beg that we may enter — because we are in — but beg that they may convert; that they may change and come back to what makes the Church.”

But the problem for the SSPX has also been that whenever the spotlight falls on them, something soon surfaces showing that resistance to change on their part is precisely the problem.

When Benedict XVI  — who courted the SSPX assiduously — lifted his predecessor’s excommunications in 2009, one of those bishops turned out to be a vehement holocaust-denier who vigorously opposed unity with the Vatican.

The views of the British ‘bishop’ Richard Williamson, who left to create one of the SSPX’s many breakaway splinter groups, showed that the traditionalists’ doctrinal rejection of the Council’s openness to other faiths at least sometimes harbors ideologies of prejudice and hatred.

Now, on the eve of a rumored agreement with Rome next month and in the wake of major concessions to the SSPX by Pope Francis recognizing the validity of its sacraments, comes a program on the same Swedish Sveriges TV channel that aired Williamson’s denial of the gas chambers.

This time, it reveals that on the issue of clerical sex abuse of minors, the SSPX has a mindset that dangerously lags decades behind the rest of the Catholic Church.

As Inés San Martín reported yesterday, the program cites both victims of three abusive SSPX priests and the response of its bishops, as evidence that the abusers were never dealt with as Catholic Church guidelines in developed countries have long required.

They were shuffled between parishes, apparently never reported to the civil authorities, and given prayer-and-penance punishments that – in one case at least – was never enforced.

Two of the abusers joined Williamson’s faction. They are in active ministry in England.

The fact that Fellay himself allowed one of the abusive priests to organize camping trips for children suggests that the culture of omertà which has caused havoc in the Catholic Church in the past reaches right to the top of the SSPX.

Almost as shocking is the revelation that the Vatican knew about these cases yet did not  — apparently  — ask the SSPX to alert the police and civil authorities in the relevant countries. The Congregation for the Doctrine of the Faith (CDF) has long urged Catholic bishops to do this as a matter of course.

Just as remarkably, the CDF urged Fellay to subject one of the accused men to a canonical trial, yet the congregation cannot have known whether such a trial would be properly or rigorously conducted.

If, as rumors suggest, the SSPX is close to accepting Francis’s renewed offer of a personal prelature — a structure that would give them a large degree of autonomy, outside the authority structure of dioceses — the pope would be advised to postpone any such deal until the traditionalists’ record on abuse has been properly examined.

The SSPX should be asked to hand over to the CDF all its files on abusive priests and any cases that have not been properly dealt with should be reviewed, and where this hasn’t happened, the Vatican should alert civil authorities. The organization should also be asked to agree to guidelines based on the template designed by the Pontifical Commission for the Protection of Minors.

Any refusal on their part to any of these requests should lead Rome immediately to withdraw the offer of a personal prelature.

Convinced that they are the guardians of timeless Catholic truth, the SSPX’s approach is to wait for the “errors” of the rest of the Church to recede into history.

“In ten years things will look different because the generation of the Council will be gone and the next generation does not have this link with the Council,” Fellay predicted in 2012.

Yet Francis — whose pontificate is firmly rooted in the Council — shows how absurd that idea is. Vatican II is here to stay. So, too, are its reforms.

Resistance to reform is one of the signs of fundamentalism. The SSPX may want to freeze Catholic doctrine at Trent, and it may — just — be possible to accommodate a group within the Catholic Church that holds those beliefs.

But an organization of 600 priests with a 1950s approach to child abuse? That Rome cannot afford.